QEvent for QGraphicsView scrollbars?

[forrestfsu]

Thanks to both of you, your answers were right on target (as usual).

I was using an event filter for other portions of my code, and wanted to keep it consistent. But the solution you showed was simple enough...and I'm definitely better off using that rather then complicating the situation.

[Bitto]

For the record, then. If you reimplement the scrollContentsBy() function of QAbstractScrollArea, you will receive the delta values from both scroll bars at once, without having to declare slots or install event filters.

void MyCustomView::scrollContentsBy(int dx, int dy)
{
    // dx = horizontal delta
    // dy = vertical delta
}

void MyCustomView::scrollContentsBy(int dx, int dy)
{
    // dx = horizontal delta
    // dy = vertical delta
}

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Btw, installing an event filter:

MyCustomView::MyCustomView(QGraphicsScene *scene, QObject *parent)
    : QGraphicsView(scene, parent)
{
    horizontalScrollBar()->installEventFilter(this);
    verticalScrollBar()->installEventFilter(this);
}
 
bool MyCustomView::eventFilter(QObject *watched, QEvent *event)
{
    bool vbar = (object == verticalScrollBar();
    bool hbar = (object == horizontalScrollBar();
    if (!vbar && !hbar)
        return false;
 
    switch (event) {
    case MouseButtonPress:
        if (vbar) { /* someone pressed the vertical bar */ }
        else { /* someone pressed the horizontal bar */ }
        break;
    case MouseButtonPress:
        if (vbar) { /* someone released the vertical bar */ }
        else { /* someone released the horizontal bar */ }
        break;
    case MouseMove:
        if (vbar) { /* someone pressed and moved the vertical bar */ }
        else { /* someone pressed and moved the vertical bar */ }
        break;
    ...
    default:
        break;
    }
}

MyCustomView::MyCustomView(QGraphicsScene *scene, QObject *parent)
    : QGraphicsView(scene, parent)
{
    horizontalScrollBar()->installEventFilter(this);
    verticalScrollBar()->installEventFilter(this);
}

bool MyCustomView::eventFilter(QObject *watched, QEvent *event)
{
    bool vbar = (object == verticalScrollBar();
    bool hbar = (object == horizontalScrollBar();
    if (!vbar && !hbar)
        return false;

    switch (event) {
    case MouseButtonPress:
        if (vbar) { /* someone pressed the vertical bar */ }
        else { /* someone pressed the horizontal bar */ }
        break;
    case MouseButtonPress:
        if (vbar) { /* someone released the vertical bar */ }
        else { /* someone released the horizontal bar */ }
        break;
    case MouseMove:
        if (vbar) { /* someone pressed and moved the vertical bar */ }
        else { /* someone pressed and moved the vertical bar */ }
        break;
    ...
    default:
        break;
    }
}

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[forrestfsu]

thanks for the eventfilter example. I noticed that the SliderReleased() signal only emits a signal for the scrollbar, not the "scroll arrow" buttons. By the name of the function, I guess that makes sense. I was wondering if there was something similar that I can call for the scroll arrow buttons. I've been digging through the QAbstractScrollArea reference, but I'm not sure if that's where I should be looking.

[Bitto]

No, I'd go for the event filter in this case.